Control system and apparatus for power generating equipment



Aug. 6, 1935. s. KERR 2,010,594

CONTROL SYSTEM AND APPARATUS FOR POWER GENERATING EQUIPMENT Filed Sept.5, 1951' 4 Sheets-Sheet 1 Aug. 6, 1935. s, E 2,010,594

CONTROL SYSTEM AND APPARATUS FOR POWER GENERATING EQUIPMENT Filed Sept.5, 1931 .4 Sheets-Sheet 2 lad/naval CL/sfomer: or Sub-Syrftm;

Q T H LgwLH 6 5120 Lin e l IN VEN TOR BY TO EY Aug. 6, 1935. s, 1 KERR2,010,594

CONTROL SYSTEM AND APPARATUS FOR POWER GENERATING EQUIPMENT Filed Sept.5, 1931 4 Sheets-Sheet 3 11v Ezvnii 2 v 5%.

lg/ 71/? ATTORNEY Aug. 6, 1935. s. L. KERR 2,010,594

CONTROL SYSTEM AND APPARATUS FOR POWER GENERATING EQUIPMENT Filed Sept.5, 1951 -4 Sheets-Sheet 4 DDUEIDEIEIDUU UUUUDEIEIDEIH [JDUDUUUDUI]INVENTOR 6. Logan /(err Patented 1935 UNITED STATES PATENT OFFICE SamuelLogan Kerr, Philadelphia, Pa.

Application September 5, 1931, Serial No. 561,460

30 Claims.

This invention relates generally to power generating control apparatusand more particularly to improved means for efiectively and economicallycontrolling a plurality of prime mover operated alternating currentgenerating units especially of the hydro-electric type.

In many of the large generating stations recently constructed theoperation of the plant is affected greatly by the many interconnectionsbetween various generating systems. Many of these interconnections arecontrolled or supplied directly from the generating plant and requiregreat flexibility in the operation of the station and impose a severeburden on the operating staii' particularly when emergency conditionsarise on one of thesystems which may be transmitted to others. Suchplants located at stra tegic points in the interconnected network mustbe capable of operating on base load with all systems in parallel or ofcontrolling speed on a large interconnected network or of supplyingfixed amounts of power to each of several systems when the varioussystems are disconnected one from the other or supplying speed controlto one system and at the same time supplying fixed amounts of power toother systems separated from the first but sometimes interconnected withthe first. There is also the requirement for reserve capacity andstandby service as well as synchronous condenser operation for powerfactor correction, all of these types of service being required from thesame plant and the same generating equipment. One purpose of the controlsystem described herein is to provide automatic means for accomplishingthe various functions outlined in order to simplify the operation of thestation, to control speed and also to control the economic loaddistribution between units as well as providing automatic means forbringing reserve units into operation without requiring the attention ofthe men on duty.

In one specific embodiment comprising a high head hydro-electricgenerating station, three major power systems are interconnected in theswitchyard adjacent to the generating plant and are under control of theoperator in the plant at the generating room switchboard. A normalfunctioning of the systems calls for the parallel operation of all threewith a fixed amount of load being fed into the network and with thevarious units in this particular plant operated on base load with theoutput economically divided between the various units. In the event ofan emergency such as a lightning disturbance or of the three systems,the interconnections between the systems will be opened automatically ormanually by the operator and simultaneously with this it is desired toredistribute the load between the various units in accordance with the Ispecific requirements of the respective systems to which they will beconnected as a result of the rearrangement of the transmission networksdue to the separation of the various systems. Each unit should supply afixed amount of load to each 10 system in accordance with therequirements of that particular system as determined by the respectiveoperating staff, the amount being determined either by verbalinstructions from load dispatchers or by contract agreements. At thesame time should anyone of the systems to which a particular unit wasassigned in this emergency program be unable to absorb the amount ofpower in accordance with the instructions or for reasons of operatingemergency or for any other reason, the speed of that particular systemwill be afiected and it would be desirable at that time to haveautomatic frequency control come into action to stabilize the speed onthat Particular system by adjustingthe output of the unit at thisstrategically located plant.

The automatic control as described in detail herein is designedprimarily for this service as the station is normally operated withthree units connected in parallel and upon an emergency occurring, oneunit will be assigned to each of the major generating networks which inturn will be separated from each other by means of the switchingequipment located adjacent to the plant. Following this segregation ofthe systems the normally interconnected control of the units will beautomatically segregated, and each unit will go over to an independentfixed load. which has been predetermined by operating instructions tothe local operating staff. If any one system cannot absorb the powersupplied to it by its unit thereby resulting in the speed (frequency)departing from normal a predetermined amount for some predeterminedperiod, the independent fixed load control load cut-out and automaticfrequency control on that particular unit will be placed in service toadjust the output of the unit to the desired amount in order to hold thefrequency at or near its normal value. All of these functions arearranged to act automatically and are described in detail herein.

In case it is desirable to operate the systems independently, thecontrol is suificiently flexible to permit each unit to be operated onindependent base load as a normal function or each unit it can controlspeed on an individual system which is separated from the remainingunits on frequency control or may be in parallel with other units whichare controlling fixed load.

An additional form of operation consists in having one unit on frequencycontrol with the remaining two units on base load control or of havingall three units on frequency control with automatic economic loaddivision maintained simultaneously.

The operation of this station also includes improved means wherebystand-by service provides reserve capacity for system operation in theevent of emergencies which occur during periods when it is undesirableto utilize flow from the station for the purpose of power generation.This condition is frequently met in hydro-electric plants having pondageor seasonal storage. For this type of operation the reserve units aremotored from the line with the hydraulic turbine runner arranged torevolve in air either by the action of automatic air vents or by thedraining of the wheelcase after the machine has been brought up tosynchronous speed and paralleled with the system. Such reserve unitsmust be operated in such a manner that the runner is kept free fromwater which requires that the gates be kept tightly closed or that thepenstock valve at the entrance to the turbine be closed and thewheelcase kept drained. In either event it will be necessary for anoperator to release the turbine gates or to open the penstock valve andprime the wheelcase before load could be picked up on this reservemachine. The automatic equipment described herein includes means wherebythe turbine casing can be primed and the penstock valve fully opened,the turbine gates released and the unit permitted to pick up loadwithout the necessity of the operator performing any of theseoperations. The initial tripping of this control equipment is arrangedto operate as a function of the system speed so that the units aretransferred from condenser service to load upon any drop in systemfrequency below some predetermined point or else by the action of theoperator in pushing a release button or by any other desirable means.

Improved means are also provided \th this automatic control so that theunits can be placed on condenser operation, the turbine gates set at afixed position, the penstock valve closed and the casing drained merelyby having the operator close a selector switch located in the controlroom, thus simplifying greatly the work which he is required to do andenabling him to have complete control over the generating unit whetherfor generating purposes or for synchronous condenser operation. withoutthe necessity of leaving the control room or of having another operatorfor this purpose.

In describing this control equipment and its various functions asapplied to the different operating arrangements, the phraseinterconnected contro will imply that it is the control equipment forthe units which is interconnected as when the generating units areconnected in parallel with the same system, but if the various units areseparated from their parallel connection with each other then thecontrol for each unit will also be segregated and each unit will operateindependently of the other, this being herein referred to as a so-calledindependent type of unit operation. It is possible, however, to operatethe various unit controls either partially or wholly independently ofeach other even though the generators are in parallel with the samesystem, this being herein broadly referred to as independent controlwhile its specific functions are defined as independent base load,independent frequency control, etc.

Other objects and advantages will be more apparent to those skilled inthe art from the followingdescription of the accompanying drawingswherein:

Fig. l is a wiring diagram illustrating one form of my invention:

Fig. 2 diagrammatically shows a power system equipped with my inventionand arranged for disconnecting the units from the line in order thatthey may be operated independently thereof and of each other;

Fig. 3 is a continuation of the form shown in Fig. 1;

Figs. 4 to 6 are diagrams illustrating modified arrangementsforcontrolling the frequency and load control impulses.

Fig. 7 is a vertical section of a turbine installation illustratingdiagrammatically various elements embodied in my improved combination.

In the description herein the various types of operations are suitably.indicated by type members although it will be understood that this ismerely for convenience of understanding.

Type 1 operation: unit No. 1 on frequency control with units Nos. 2 and3 on base load contr0Z.--In this operation units Nos. 2 and 3 aremaintained at a constant combined output (base load) while the output ofunit No. i is varied to maintain constant station frequency, it beingunderstood that all three units are in one station although it may beconsidered in the broad aspect of the invention that each unitrepresents a station by itself and that the three units are connected inparallel to a common system. In accordance with previous applications ofmine theconstant fixed load is economically distributed between the twounits in accordance with their respective operating characteristics. Asexplained in said applications the units may have similar or dissimilarcharacteristics but in either case the load is automaticallyeconomically distributed between the two units.

Base load control of units 2 and 3 will be first described and then thefrequency control of unit i will follow. A master selector switch S(left side Fig. 1) is placed in position i. This switch consists of aseries of individual switch sections ai. Each section is enclosed by adotted line box and has four contacts diagrammatically shown asconcentrically arranged about a central pivot of a suitable switch arm(not shown) which is adapted to selectively engage any one of theconcentric contacts. The switch arms of each switch section areconnected together by a common operating means (not shown) so that allswitch arms are in the same position for anyadjustment of the switch.The lowermost contact in each box is position i and the next contactposition 2, etc. The type of switch used in actual practice may be anyof the commercial forms of transfer switches one of which isspecifically referred to in my copending application filed March 26,1931, Serial No. 525,355. A unit selector switch S (the single primerepresenting unit No. i) is placed in position 3. This switch is of thesame general type as the master selector switchS except five concentriccontacts are shown. The first contact, however, represents an o positionso that position No. i is the second contact from the bottom of eachbox, position No. 2 the third contact, etc. Unit selector switches S"and s'" I, this position being also the second contact.

from the bottom of each dotted line box. These switches are also of-thesame general type as the master selector switch 8.

In this present description it will be assumed that the system is inoperation and that each unit; preferably of the hydro-electric type, isprovided with an electric generator 4 driven by a hydraulic turbinegenerally indicated at 5, Fig. 6, the turbinehaving an inlet casing, arunner and adjustable turbine gates, all as well understood in the art.In accordance with usual practice, the turbine gates are adjusted by aservo-motor 8 which in turn is controlled by a speed responsive governor'I having a usual synchronizing or load adjusting motor 3i, Fig. 1. Thisload adjusting motor and its functions are well known in the hydraulicturbine artand its use in the general type of automatic controlequipment here being considered was described more in detail in mycopending application, Serial No. 408,544 filed November 20, 1929. Hencea detailed description is not necessary here and it will sufllce tostate that when the motor is operated in one direction or the other thegates of the turbine, or the control valves such as are used with othertypes of prime movers, are actuated so as to increase or decrease thepower input to its unit, the direction of rotation depending uponwhether raising or lowering control impulses are transmitted to the loadadjusting motor. These control impulses are of two kinds, one forfrequency control and the other for load control and each one is adaptedto effect both raising and lowering. of the load adlusting motor. Assimilarly described in said copending application the functions of myimproved automatic equipment herein described are also superimposed onthe normal functions of the governor.

It will be assumed that the units have similar operating characteristicsso that, for instance, the most economic load distribution between units2 and 3 requires equal loading. To maintain a fixed combined output orbase load on these two units there is provided a single master loadsetter for cooperation with all units and unit load transmitters one foreach unit. Each unit transmitter is balanced against the master loadsetter so that upon occurrence of any unbalance a galvanometercontrolled circuit causesjcontrol impulses to be transmitted to the loadadjusting motors. This particular arrangement has been described indetail in said copending application, and hence it will suffice tobriefly point out here only the general features of such an arrangement.Units 2 and 3 are provided respectively with these unit loadtransmitters in the form of potentiometers or resistances l0" and 10",each rotatably actuated by a wattmeter of their re- .spectiveunits inthe manner described and shown in my other application. A master loadsetter i2 is in the form of a manually operated rotatable resistance.One side of the resistances l2, l0" and W are connected together toinsure, as by a wire IS, the same potential at that end of eachresistance. The other end of each resistance is connected to individualtransformers such as l5, II" and lif", the primariesof each of which areconnected across the same phase of the A. C.

supply (upper left side of Fig. 1) The potential of each transformer isthe same so that the potential across each resistance is also the same.A galvanometer circuit for unit 2 is bridged from a slide contactfll'to. a slide contact I. of the master load setten this circuit passingfrom contact 11" through galvanometer 18" thence to and acrossselectorswitch Sa in position I, to

the left along wires {land 2| to switch So in position iand thence toslide contact H of the master load setter.

A similar galvanometer bridge circuit for unit 3 is provided betweenslide contact l8 of the master load setter and slide contact 11" of theunit load transmitter "1", this circuit extending from slide contact ilthrough galvanometer W to S"g in position! connected to common wire 20,which then follows the same circuit as just previously described for thegalvanometer i9".

Assuming that this type 1 operation requires a given combined output onunits 2 and 3 the operator manually adjusts master load setter I! inaccordance with suitable graduations on a dial 'bined load is increasedor decreased, contactmaking devices 23 and 23 will operate to causecontrol impulses to be transmitted to their respective load adjustingmotors thereby adjusting each unit to increase or decrease its poweroutput in accordance with the setting of the master load setter. As theload on the respective units is adjusted their respective wattmeterswill cause resista'nces l0" and lil' to be actuated until positionsthereof are reached which will cause a balanced potential between thecontacts l8, I1" and i1" at which time current will no longer flowthrough the bridge circuits and the galvanometers will remain in theirneutral position.

The contact-making mechanisms 23" and 23 and also 23' to be mentionedlater are each of the type more fully described in my copendingapplication, Serial No. 408,544. It will sufiice to point out here thatwhen the potential at either transmitted through these wires becomecorrespondingly shorter until finally no contact is made therebyindicating that the unit is properly adjusted.

The circuit for wire 24" and 24" is from the main D. Q'supply lead 25through relay 28,

28 (lower right'corner Fig. l) across the upper right contacts of thetwo-way switch 26 to wire 21 leading in common to each of thecontactmaking devices 23" and 23. The wire 24" is connected acrossswitch Sh in position i and thence down. to the coil of relay 28'',across the closed left contacts of switch 29" to the other side of theD. C. supply line 30 which is connected as by wire 3| through aprotective circuit to be described later and to the main D. C. supplyswitch 32. Energization of coil relay 28" closes its contacts whereuponthe load adjusting motor 3| is rotated in a direction to lower the loadon its unit. The motor circuit is from D. C.

supply line 25 through a manually adjustable resistance 32" acrosscontacts of relay 28" and through the lowering (left) field of motor.3l"to the other side of the D. C. supply line 33.

If the difference in potential between contacts l8 and I1" requires anincrease in load then contact-making device 23" intermittently closes acircuit through a wire 34" which is connected across switch 8" inposition i and thence down tothe coil of relay 35" the remainder of thecircuit for which is the same as for wire 24". Upon energization ofrelay 35" its contacts are closed whereupon current is supplied to theraising (right) field of motor 3|" as from the D. C. supply line 25through the resistance 32" and on to the other side of the D. C. supplywire 33. The motor will thereupon be actuated to raise the power outputof the unit until no difference in potential exists between contact H"and H8.

The same general contact-making and relay control circuit is used forload adjusting motor Bl' in that the wire 24" is connected throughswitch S"'h in position I and down to the coil of relay 28" and acrossthe closed left contacts of switch 29. to the other side of the D. C.supply. Energization of relay 28" establishes a circuit from 'D. C.supply line 25 through resistance 32" across the closed contacts ofrelay 28" to the lowering field of the load adjusting motor 8V.

The other wire 34" is connected through switch S"'f in position I andthence down to the coil of relay 35" to the other D. C. supply line 30.Closure of the contacts for this relay establishes a circuit through theresistance 32" across the closed contacts of 35" to the right or raisingfield of load adjusting motor 3l-".

From the foregoing description it is seen that.

when the master load setter I2 is set for a fixed total output of units2 and 3 the galvanometer l9" and l9' of these units will be actuated inaccordance with the potential difierence not only between contacts H"and IT with respect to contact I8 but also of contact H" with respect tocontact ll or vice versa. If any difference in potential exists betweencontact H" and 81" the units will be adjusted with respect to each otherso as to raise the load on. one and decrease the load on the other untilthe outputs of these units will equal the total combined output desired.If the units are of dissimilar characteristics the resistances ID or i imay have portions short-circuited substantially in accordance with thecharacteristics of their respective units all as described in mycopending application Serial No. 408,544.

Type 1 operation (contd) frequency control by unit No. 1.-In thisfurther phase of type I operation unit l is used to control frequency ofall the units while at the same time the base load units are operated togive a fixed combined output as just described. To control frequencyhowever it is necessary to vary the output of a unit in accordance withfrequency variations and to accomplish this it is necessary to permittransmission of only frequency control impulses to the unit and pre enttransmission of load control impulses. To do this the load controller L'is prevented from transmitting'its control impulses to the loadadjusting motor 3! of unit I due to the fact that wires 24' and 34' areconnected to switches S'h and 1 respectively each of which rests upon anopen contact in position 3.

The frequency controller F is of the type having an impedance bridgewith a galvanometer .31. This bridge and the galvanometer field aresupplied from an A. C. source 38' one wire, of which leads directly fromthe switch to both the impedance bridge and galvanometer field while theright hand wire from switch 38 is connected as by wire 39 to switch S'cin position 3 and thence to the impedance bridge and galvanometer field.Upon variations of frequency from normal the galvanometer 31' will causeactuation of contact-making device 40' so as to increase or decrease theoutput of unit l in accordance with whether the frequency variation isabove or below normal. This contact-making device with its continuouslyoperating motor 4| is of the same general type used in the loadcontrollers. The result is that if the frequency rises galvanometer 31'swings so as to cause intermittent control impulses to be transmittedthrough wire d2 across switch S'd in position 3 and thence down andacross by wire 43' to the coil of relay 26' the circuit for which iscompleted across the left closed contacts of switch 29 to the D. C.supply line 3!]. Closure of contacts of relay 28' establishes a circuitfrom D. C. supply line 25 through resistance 32 across contacts of relay28' to the left or lowering field of motor 3i and thence to the otherside 33 of the D. C. supply. This lowers the power output of unit I andthus corrects the frequency.

If the frequency should drop below normal .thereby necessitating anincrease in power, then control impulses would be intermittentlytransmitted through wire M across switch S'e in position 3 and thencedown to wire 55 to the coil of relay 35' and thence to the other side ofthe D. C. supply line 30 in the same manner as for relay 28.Energization of relay 35 establishes a circuit from resistance 32'across the relay contacts and. to the right or raising, field of motor 3I and thence to the other side of the D. C. supply line 33. The outputof unit I is thereupon raised so as to correct the frequency. Thecharacteristics of the contact-making device do of the frequencycontroller in gradually diminishing the extent of each control impulseis the same as with the load controllers thereby insuring stableoperation of the equipment.

Type 2 operation: control of all units intercom nected on station baseloaaL-In this operation the total station output is maintained at afixed value and the load equally distributed between the units, assumingthat they each have identical with units 2 and 3 operating with acombined fixed output the unit transmitter resistances l8" and IO arebalanced against the master load setter l2. In order to have unit No. lsimilarly operated in this combination its unit load transmitter I0 isconnected in parallel with the other transmitters It and lll' and allthree are balanced against the master load setter l2. To accomplish thisthe master selector switch S and each of the unit selector switches areall placed in positionZ. This causes the load controllers for each unitto be interconnected and also causes disconnection of the frequencycontrollers. Assuming that the master load setter I2 is readjusted bythe operator so as to increase or decrease the total station output thena difference in potential will exist between the master slide contact i8and each of the unit slide contacts. Taking first the difference inpotential between the master slide contact l8 and the unit slide contactH the galvanometer IQ of the load controller L will be deflected bycurrent flow in the galvanometer bridge circuit which extends from slidecontact I? through wire 41 to galvanometer l9, thence to switch S'g inposition 2 and across characteristics. As previously described,

the'contacts of relay ll normally closed when deenergized, thence acrossthe lower right pair switch S"o in position 2, thence across contacts ofrelay .8" normally closed when deenergized,

and across the lower right pair contacts or relay 49" normally down whendeenergized thence up to wire 20 and down to wires 50 and 2! and thenceon as previously described to master contact 'll.

The bridge circuit for unit 2 is now from unit slide contact Il' throughgalvanometer l8' across switch S"'a in position 2, across contacts ofrelay 48' normally closed when deenergized, and thence up and acrosslower right pair of contacts of relay 49" normally down whendeenergized, thence up along wire M to wires 50 and 2t and on to mastercontact l8.

It will be noted that one end of unit load transmitter III is connectedto the wire commonly connected to one end of each of the other unit loadtransmitters, this in order to maintain the same potential on each,while the other end of the transmitter I0 is connected to a. potentialAs a result the units will all be adjusted to the same output because ifany dif- Ierence in potential exists between any pair of contacts theoutput of the respective units will be raised or lowered as is necessaryto establish equal loading.

Type 2 operation (contd): one or more units are disconnected from systemline to supply a. customer independently (either base load or frequencycontrol); other units remain connected to system line but each of theseunits is transferred toits own independent base load-As shown in Fig. 2the three units are connected to a system line designated as such andthree customers such as a city, town, manufacturer or the like are alsoshown connected to the system line. If the power demand by one customershould fall below a predetermined value it is desired to disconnect thatcustomer from the system line and supply current from an individualstation or unit. This is desirable in order to maintain the maximumcombined efliciency for the system, it being understood that it is moreeflicient to operate the remaining units at their Q point of maximumefliciency and allowing possibly the one unit which is independentlyconnected to the one customer to operate at a. lower eillciency. On theother hand it might be that when one customers power demand exceeds apredetermined amount it is also desirable to supply him from anindividual plant entirely disconnected from the system line.

It is further desirable upon disconnecting any one unit from the systemline in order to supply the independent customer, to place each of theremaining units on unit base load, that is, each unit will be controlledso as to give a fixed unit output irrespective of the fixed output forwhich another unit might be adjusted. With this arrangement the totalstation output or station base load is not maintained in accordance withthe setting or the master load setter I2 but must -now be regulated foreach unit alone.

grammatically indicated at 53, Fig. 2. Upon opening of the circuitbreaker a switch 54 is closed, (Fig. 2 and near bottom left corner ofFig. 1) this switch being suitably mechanically or otherwise connectedto the circuit breaker to compel closing or switch 54'. Closure ofswitch 54 causes each unit to be placed on independent base load. Thecircuit is established from. one side oi. the D. C. line by a wireleading from the right contact of switch 54 down to line 33 and a wireleading upwardly from the left contact to relay 49 which is connected tothe other side of the D. C. supply. A wire also leads downwardly fromthe left contact of switch 54 from which a wire 55" leads upwardly torelay 49" which is connected to the other side of the supply line 25.Also, a third wire 55" leads up to relay 49" which also is connected tothe other side of the D. C. wire leading downwardly to wire 25. Thusrelays 49', 49" and 49 are energized and moved to their up position. Asa result the slide contact l8 of the master load setter is disconnectedfrom the galvanometer circuits for each unit and the unit load settersare substituted.

The function of the unit load setters is to each unit what the masterload setter is to the combined units, so that a fixed output of eachunit may be established independently of the other units. The unit loadsetters are indicated at 56', 56" and 56". In unit I, slide contact I1is now connected to a slide contact 51', this circuit extending awayfrom contact I1 to wire 41 through galvanometer l9 across switch S'g inposition 2 and across contacts of relay 48' still in its downdeenergized position and thence across the upper right pair of contactsof relay 4!! and thence upwardly along wire 58 to slide contact 51. Itis thus seen that for any fixed adjustment of unit load setter 5B thegalvanometer will respond in accordance with any difierence in potentialbetween slide contacts 51' and I1 thus causing a contact-making device23 to transmit control impulses either to the lowering or raising relays28 and 35 of the load adjusting motor 3i all as previously describedwith type 1 operation.

The bridge circuit for unit 2 is similar to that just described, in thatit extends away from contact ll through g'alvanometer [9" across switchS"g' in position 2 andacross contacts of relay 48" still deenergized ina down position, thence across upper right pair of contacts of relay 49"to wire 58" and slide contact 51". established from slide contact l'lthrough galvanometer l9 across switch S"'g in position 2, contacts ofrelay 48" and upper right pair of con- A similar circuit is tacts ofrelay 49" to wire 58" and slide contact 51". It is thus seen that theoutput of the respective units l-3 can be in any desired ratio.

Subsequent disconnection of another unit from the system line in orderto supply anothercustomer independently does not effect any furtherchanges in the unit base load circuits just described because uponopening of a circuit breaker such as 53 for unit 2, Fig. 2, controlswitch 54" (bottom Fig. 1) will simply establish the same circuit fromD. C. supply line 33 to the wires 58, 55" and 55 as was established byswitch 54', It is seen, however, that if units Nos. i and 3 aremaintained connected in parallel to the system line and should it bedesired to disconnect unit No. 2 therefrom, then switch 54" willfunction to place each unit upon independent base load. It will ofcourse be understood that switches of the general type 53, 54 could beapplied to each unit if desired but for purposes of modification, unitNo.3 in Fig.

2 has been shown without such a switching arrangement.

Automatic frequency control the independent systems :iust described:automatic transfer from wait base load to lrequency.--If the frequencyvaries on an independent system, the frequency controller of the unitwhich supplies that system will be automatically brought into operation,the unit thereafter not being on base load. If two or more units areconnected in parallel and are on unit base load, the frequencycontroller of these units cannot be brought into operation uponvariation in frequency, this variation being corrected by other plantsor units assigned for this purpose.

Considering unit No. l which is assumed to be the independent unit, whenits frequency varies a certain predetermined amount from normal (upperleft corner Fig. l) a frequency relay W is actuated so that its contactbar tilts in one direction or the other, depending upon the direction ofvariation from normal, to close one or the other pairs of contacts,thereby energizing time delay relay 63' by a circuit extending from theright side of the time delay relay coil down to the left side of A. C.supply switch 38' while the right side of this switch is connectedacross the left upper pair of contacts of relay 69' and thence to wire62' which is connected to the lower set of contacts of frequency relay6b, the upper ones of which are connected to the coil of time delayrelay 86'. If the frequency variation continues for a predeterminedlength of time as established by the time delay relay, the switch ofthis relay will close thereupon connecting the direct current supplyline, shown in heavy lines as leading from D. C. supply switch 32 (lowerleft corner Fig. 1), to energize relays 53', 68' and 64' connected inparallel across the two D. C. supply lines, one of which is 25. Relays83' and or when energized are raised to their up position and are of themanually releasable type, whereby upon return to normal frequency theywill remain in their up .position unless manually released. Upon raisingof relay 63' the lower left contacts break the circult through switchS'f in position 2 to which wire 3| of the load controller is connectedand similarly the lower right pair oi contacts of relay 63' break thecircuit through switch S'h to which wire 24' of the load controller isconnected. However, when the relay is thus raised the frequencycontroller is connected by wire 58' leading from the frequencycontroller through switch 5's in position 2, across upper left pair ofcontacts of relay 83' and then along wire 66' to wire -35 which isconnected to the raising relay coil 35' of the load adjusting motor. Thefrequency controller is connected across switch Sd in position 2 to theupper right pair of contacts of relay 63' and thence over and down towire 43' connected to the lowering relay 2B.

When relay 63' is raised the circuit of the load controller motor 61' isbroken by reason of the circuit for this motor having a wire leadingdownwardly therefrom across switch S'a in position 2 to the lower rightpair of contacts of relay 64 which by now being opened breaks the normalcircuit which otherwise continues down to the main A. C. supply line 68.However, when relay 64 is raised the circuit for the frequencycontroller motor ll is established in that the circult from the lowerside of motor 4| is connected to the wire leading upwardly to the mainA. 0. supply while the top side of said motor is connected across switchS'b in position 2 to the upper right pair of contacts of relay 64 andthence downwardly to the A. C. supply wire 88. At the same time the A.C. current supply for the impedance bridge and field of gaivanometer 31'is established from the left side of A. C. supply switch 38' down. tothe galvanometer field, thence across switch Sc in position 2 and acrossleft upper pair of contacts of relay 6% and thence upwardly along wireas to the right side of A. C. supply switch 38'.

If it was a decrease in frequency which caused the frequency relay to toclose, then the contact= making device ill of the frequency controllerwill transmit intermittent control impulses along wire 64! to theraising relay 35' thereby raising the output of unit No. l toreestablish normal frequency. An increase in frequency would cause thecontrol impulses to be transmitted over a wire 412 from the frequencycontroller and thence down to the lowering relay 28' to decrem the unitoutput and thus correct the frequency. An independent base load bridgecircuit is disconnected upon energizing and raising of relay 48, itbeing remembered that this relay is inserted in the bridge circuitconnecting slidecontacts ll and 5? through galvanometer i9.

Upon reestablishment of normal frequency which may be accomplished afterthe disturbing cause has been removed or the load sufiflclentlystabilized the operator releases relay 4!, 63' and 66', therebydisconnecting frequency controller F and again connecting the loadcontroller L with the independent unit load setter 58' and loadtransmitter ill.

When unit 2 is disconnected from its parallel operation so as to operateindependently, it will then be subject to frequency control throughoperation of frequency relay 6B" the circuit for which is substantiallythe same as that for relay 88' and may be briefly described as follows:Starting from bottom Fig. 1 at center the left contact of the A.- C.supply switch 38" is connected by wire 12 to one side of the coil oftime delay relay 65" the other side of which is connected to the uppercontacts of the frequency relay Bil", the lower contacts thereof beingconnected to wire 62" thence across the upper left pair of contacts oi.relay 49" and along wires 13 and 18 which are directly connected to theright side of A. C. supply switch 38". The various coils of frequencyrelay 6B" and of the other frequency relays are energized by the A. C.supply connections clearly shown. The frequency controller F" isconnected and the load controller L" is connected in the manner asdescribed for unit No. I and similar connections for both the frequencyrelay and the frequency controller F' and load controller L' aresubstantially the same as for the other units so that a detaileddescription of the wires is not necessary. It will of course beunderstood that the relays for each unit corresponding to relays 48',63' and 64' are of the type requiring manual resetting and in all otherrespects are also the same.

Certain of the automatic-transfer operations hereinbefore describedunder type 2 may be effected manually, and therefore permanently, in themanner to be hereafter described under types 4, 5 and 8.

Type 3 operation: all units under interconnected control with economicload distfibution and with all units receiving frequency controlimpulses transmitted from any one frequency cont1oZler.--In thisoperation master selector switch S is in position 3 and each of the unitselector switches is in position I. lfn'this case the wattmeter operatedload tra usmitter resistances I 01, I and III are balanced against eachother through the galvanometer bridge circuits for the loadcontrollers'of the respective units except that the galvanometer circuitfor load controller of unit No. I is shunted out thus permitting thefrequency controller of this unit to effect the primary control ofoutput thereof. During this operation the master load setter is entirelydisconnected and the frequency controllers for units Nos. [and 3 arelikewise disconnected. The frequency controller for unit No. I ismaintained in operation simultaneously with the operation of the loadcontrollers of units 2 and 3. The frequency controller in operation isso arranged with respect to the load controllers in operation that theirrespective control impulses will not interfere with each other. It willof course be understood that instead of selecting the frequencycontroller of unit, I any other frequency'controller might be employedif desired by making connections (not shown) similar to those at presentemployed for the frequency controller of unit I, but in this case the.load controller corresponding to the frequency controller to be usedwill be disconnected.

The disconnection of master load setter upon setting of the selectorswitches is seen by the fact that the wire leading to the slide contactI8 has no connection to the master selector switch S9 in position 3. Thegalvanometer I9 for the load controller L is shunted out by wiresleading upwardly from the galvanometer I9 to switch S'y' in position I,thence through wire 2 I, across master switch So in position 3 to wire41 connected to the other side of galvanometer I9. The unit loadtransmitter resistances are balanced against each other in that thepotential connections to each end of the resistances are the same aspreviously described it being noted that the circuit leading away fromslide contact II' extends across master switch Sg in position 3 to wire2I upwardly along wire 50 to wire 20, along this wire to a wire leadingto unit selector switch S"g in position I and thence across to thegalvanometer I9" from which the circuit continues upwardly to slidecontact ll" of the load transmitter of unit 2. Similarly a wire 20 isconnected across switch S"g in position I to galvanometer I9' and thenceupwardly to slide contact II' of the load transmitter of unit 3.

The frequency controller F" is disconnected when section 0 of switch S"is in position I thereby disconnecting the galvanometer field thereof,whereas sections d and e disconnect the contactmaking device 40" andsection b also when in position I disconnects the operating motor 4|" ofthe contact-making device. Similar disconnections are effected for thefrequency controller F.

Frequency controller F of unit I is maintained in operation in thefollowing manner. The galvanometer field circuit extends from the leftcontact A. C. supply switch 38' downwardly to the galvanometer field,thence through unit selector switch S'c in position I and over to masterselector switch So in position 3 and thence around and upwardly alongwire 38 and over to the other side of the A. C. supply switch 38'. Itwill of course be understood that the A. C. supply switches 38, 38" and38" while connected to their respective units are nevertheless connectedto the system line when the units are connected in parallel operation,thus insuring that the frequency imbetween the units. I are transmittedalternately with the frequency pressed upon frequency controller F isthat of all of the units or system rather'than Just one unit. Theindividual A. Q. supply switches permit the unit frequency controllersto be responsive to the frequency of each independent unit when the unis are not connected in parallel.

The circuit for frequency controller motor 4| includes a wire extendingupwardly and to the left from said motor, thence across unit switch 8'!)in position I, across master switch Sb in position 3 to the other sideof the A. 0. supply line 68. The load controller L is maintained inpartial operation by having its motor 61 continuously operated due tothe circuit contin ring from the motor down and over to unit switch S'ain position I and thence across master switch So in position 3 and tothe main A. C. supply line 68. Operation of motor 61 causes continuousoperation of the contact-making device 23' but due to galvanometer I9being shunted out the normal contact-making element will not be closedat any time. However, there is mounted upon the continuously rotatingcamshaft two special contacts diagrammatically indicated at IT and 18.Similarly identified contacts are provided for the load controllers L"and L all of which are connected to common wires I9 and 80. of thesespecial contacts is to insure that frequency control impulses fromcontroller F will not overlap or interfere with load control impulsesfrom the load controllers L" and L'.

The circuit for contact-making device 40 is supplied from one side ofthe D. C. line by wire 21' which is connected also (lower right cornerFig. 1) across switch 26 in its up position to D. C. supply line 25. Thecircuit when closed through wire 42 is connected across unit switch S'din position I, master switch Sd in position 3 and thence along wire I9to contacts I8, 18' and 18", a return circuit from these latter contactsbeing through wire say 24', across switches 8% in position I and masterswitch Sh in position 3 and thence down to wire 43 to lowering relay 28of the load adjusting motor 29'. The return circuits for contacts 18 and18" are through wires 24" and 24" respectively, these connecting throughthe unit selector switches Sh and S"'h each in position I and thencedown to the lowering relays 28 and 23". It is thus seen that if thesystem frequency should rise thereby closing the circuit through wire 42of the frequency controller F the frequency control impulses would betransmitted through contact I8, 18" and 18" to the lowering relays toeach load adjusting motor, thereby tending to return the frequency tonormal. However, it may be that each unit will not be adjustedidentically or to the same extent each time a control impulse isimpressed upon their load adjusting motors with the result that the loadwill not be equally distributed between all units for maximum combinedeinciency. In this case the output of the units being different thewattmeters will cause different adjustments of the loadtransmittingresistances III, etc. and accordingly cause differences in potential between their slide contacts II, etc. with the result that load controlimpulses are now impressed upon the respective units so as to equalizethe output The load control impulses control impulses for the reasonthat the cams for the special contacts I8, etc. are angularly displacedfrom the cams for the normal contacts by say, 180.

The load controller L of unit I merely trans- The purpose' mitsfrequency control impulses to this unit through the special contacts andno load control impulses are necessary because this unit is usedprimarily for frequency control. The other two units are readjusted uponany variation in output of unit I so as to obtain economic division ofload between all units, this division of load being effectedautomatically through the load controllers of units 2 and 3 andassociated circuits.

The contact-making camshafts of each of the load controllers are shownas being mechanically independent of each other although under certainconditions of operation it is desirable to have these camshafts eitherelectrically or mechanically connected so that they will all have thesame phase relation, thereby insuring that frequency control impulsesare simultaneously transmitted to each unit followed by load controlimpulses being simultaneously transmitted to each unit. This synchronousrelation of the shafts may be effected either electrically as by havingthe motors 6?, etc. of the synchronous type and arranged to bemaintained in the same phase relation at all times orof having saidmotors mechanically arranged as by a common camshaft in which case thecontact-making devices of all load controllers would be continuouslyrotated throughout operation of the control equipment. This, however,would not necessarily mean that control impulses would be continuouslytransmitted to each unit if such were not desired because bydisconnection of the galvanometer circuits of the frequency and loadcontrollers for the particular unit to be disconnected impulses wouldnot be transmitted. Such a mechanical connection between the camshaftsis shown in my copending application Serial No. 525,355, filed March 26,1931.

Type 4 operation: interconnected control of all units for station baseload without automatic transfer to either frequency or independentload.- In this operation it is desired that a fixed total output of thestation shall be maintained irrespective of changes in load demand orfrequency variations within certain limits. If for any reason thefrequency variations are greater than the permissible limits then aprotective circuit automatically disconnects the entire automaticequipment, whereupon each unit is under the control of its individualspeed governor in the same manner as is usual in the ordinary operationof hydro-electric units. matic equipment is thus disconnected the unitsvof course may or may not remain connected in parallel depending upon thecondition of operation. To accomplish this fixed station output themaster load setter l 2 is adjusted for the given station output,whereupon the unit load transmitter resistances l, etc. automaticallyequalize the load between all of the units so as to maintain the givenoutput. In this case the master selector switch is in position 4 and theunit selector switches are each in position l. I

The operation and circuits for the load controllers L" and L' are thesame in this type 4 operation as they were for type 3 operation in thatin each case the unit selector switches are in position' I; thus theload controllers are in operation and the frequency controllers aredisconnected. However, for unit' l it is now necessary to disconnect thefrequency controller and also disconnect the shunt around thegalvanometer I9 01 load controller L to thereby reconnect galvanometerIS in the bridge circuits of the When the auto master load setter andtransmitters. This is done when master selector switch is moved to itsposition 4 in that the circuit for galvanometer I8 now extends upwardlytherefrom to switch S'g in position i and upwardly to wire 2| acrossmaster switch So in position 4 and thence upwardly to master load setterslide contact l8 while the circuit leads from the other side ofgalvanometer l9 upwardly along wire ll and thence over to slide contactIll. The shunt circuit which leads in the other direction from wire lland connected to section 9 of master switch S is broken therebydisconnecting the galvanometer shunt.

The frequency controller F is disconnected in that the wire leadingdownwardly from the galvanometer-field and across switch Sc in positionI is disconnected in position of the master load setter. The frequencycontroller motor is also disconnected by movement of section b of masterswitch S to position s. The lowering and raising contact circuits as and62' of the frequency controller are also broken by master switch Sd andSe each in position *3.

The control impulses will now be transmitted to the lowering and raisingrelays of each unit in the manner as previously described with otheroperations.

Type operation: all units connected triparallel with. independent unitbase loud control- In this operation the master selector switch may bein any of its four positions but the unit selector switches are inposition 5. This results in the galvanometer circuit for each loadcontroller being bridged across the unit load setter, and unit loadtransmitter of only its respective unit. All frequency controllers aredisconnected. The galvanometer circuit for the load controller nowextends from slide contact ll of unit load transmitter i ll over to andalong wire 67 to galvanometer l9 thence upwardly to unit selector switchSg in position t and thence upwardly along wire 58' .to slide contact51' of the unit load setter 56'. The load adjusting motor relays 28' andwill now respond only to load control impulses caused by variations fromthe fixed output of this particular unit alone. The galvanometer circuitfor the load controllers of the other two units are similarlyindependently bridged across contact I?" and 51", and l1"' and 51".

As a result the unit load setters may be adjusted for unit outputsindependently of each other. The general mode of operation of this typeis the same as the independent base load control of type 2 operationwith the exception that the automatic transfer provisions aredisconnected in the type 5 operation.

Type 6 operation: each unit independently con.- nected to a separatesystem with. manual establishment of independent frequency control foreach unit.To disconnect the parallel operation of the units so that eachunit can independently supply separate customers or systems and at thesame time maintain normal frequency on each' separate system unit,selector switches are placed in position 3 while the master selectorswitch may be in any position. The load controllers for each unit arethus disconnected and the frequency controllers are connected to theirrespective units independently of each other. In this case thegalvanometer circuits for the frequency controllers are connected to thesystem which the particular unit is supplying. For example, the field ofgalvanometer 31' unit No. l is connected to the left contact of the A.C. supply switch II while the other side of this switch is connectedthrough wire 39 to unit selector switch S'c in position 3 and thence tothe other side of the galvanometer field. The frequency controller motor4| is also connected by the wire leading upward therefrom to selectorswitch S'b in position 8 and thence downwardly to the main A. C. supplyline 68, it being understood that the diagram of Fig. 2 is nowapplicable to the parallel system. The corresponding circuits for theother units Nos. 2 and 3 are the same as for unit No. I while thetransmission of frequency control impulses to the load adjusting'motorrelays is the same as previously described with other operations. 0!course when each unit is disconnected from the parallel system andconnected to its independent system the switches 54', etc. are closedwith consequent energization of the sets of relays such as 49', 48', 63'and 64 as was the case with the automatic transfer but the closing ofthese relays in this type 6 operation does not in any way affect theoperation because the return wire from each of the relay contacts to theselector switches is connected to an open contact.

Protective circuit.As described in my other copending applications it isdesirable to disconnect, preferably automatically, the automatic controlequipment when changing from one type of operation to another or uponoccurrence of any abnormal conditions arising in the control equipmentor system.

The protective system as applied to the present application consists inhaving the plus side of the D. C. supply from switch 32, lower leftcorner Fig. 1, connected across the upper right pair of contacts ofrelay 85. This relay is energized by current supplied through a circuitwhich is connected in series through various instruments and sections ofthe selector switches which, if in normal operation or condition, willcause energization of relay 85 and closure thereof in up position,thereby supplying current to the control equipment. This circuit extendsfrom the plus or left side of D. C. supply switch 32 across contacts ofrelays 86 and 81 and thence upwardly from relay 81 to a set of specialcontacts in a frequency recorder FR. which as described in my otherapplications are adapted to open upon a predetermined high or lowfrequency. The circuit continues from these contacts to the left side ofa high and low load-limit switch 88. The elements above and to the rightof the dotted square FR, Fig. 1, connected to the load recordergenerally shown at 88, are identical with the mechanism generally shownat 480 in Fig. 4 of my copending application, Serial No. 408,544, andhence will not be described in detail in this application. A motor 88adrives the recorder 88 whose galvanometer field I84 is supplied withpotential from a transformer 88b. The recorder 88 specifically is a highand low load limiting device interconnected with a protective circuit insuch a manner that a continuous circuit is made through a selectorswitch 880 to wire 88 and thence to master switch Si. The connectionthrough the selector switch 880 is maintained provided that the outputof the station within certain given limits determined by the setting ofthe selector switches. When these limits are exceeded, the circuit isopened, thus tripping protective relays as herein described to cut oifthe power from the control circuit until reset by the operator. Themaster switch Si when in position 2 (as in type 2 operation) will beconnected to the wire leading from relay 81, thereby shunting out thespecial contacts of the frequency recorder and also the high and lowload-limit switch 88 as the operation of these two instruments is notdesirable during this type of operation.

While these two instruments are thus shunted out the protective circuitcontinues on through wire 88 to unit selector switch 8'1 and in eachposition thereof, except No. I, the circuit continues over to switch8"9' from which in any position thereof, except No. I, the circuitcontinues over to switch S":i. The circuit continues on from this switchbut it is desired to revert first and consider other positions of themaster switch Si. Positions I and 3 of the selector switch are connectedthrough S'i, over to S"i and thence to S"'i which is connected to thecontacts of section 7 of switch S'. Returning again to master switch Siin position 4, this is connected to S'k, over to S"k and thence to S"'kwhich is also connected to the contacts of sections 9' and i. Thecircuit from these three sections continues out through wire 9| tonormally closed push button switches 93, across the upper left pair ofcontacts of relay 94 through the coil of this relay and back to theright side of the D. C. supply switch 32. Relay 85 is also connected inparallel with relay 94.

Due to any one of the following causes the protective circuit will bebroken: Failure of any of I the phases of the A. C. supply which willcause relay 86 or 81 to become deenergized, thus breaking the circuit tothe positive D. C. Upon occurrence of abnormal frequency the contacts inthe frequency recorder will open the protective circuit. If the stationoutput exceeds or falls below the settings as indicated on the high andlow loadlimit switches, this circuit will be broken. Upon any change inthe settings of the selector switches S, S" and S', the circuit will bemomentarily bro-ken, thereby deenergizing relays 94 and 85 which remainopen because the supply comes through the upper left contacts of relay94. The protective circuit can also be broken manually by the opening ofthe push button switches 93. In order to again close the protectivecircuit it is necessary to close the push button switch 98 whichenergizes relays 88 and 85 by completing a circuit from the left side ofsupply switch 32 across contacts of relays 86 and 81 which are normallyclosed, providing the A. C. supply is maintained. The circuit thuscontinues from relay 81 down through the normally open switch 86 toenergize. relays 84 and 85 whereupon their contacts will be closed toreestablish the protective circuit, providing the condition which causedthe protective circuit to be disconnected has been corrected. If theabnormal condition still exists relays 94 and 85 will be immediatelyreleased, providing of course that the operator has removed his handfrom switch 98. If desired switch 95 may be of the type which may beclosed momentarily but not held closed, thereby preventing the operatorfrom holding the protective circuit in against the action of theabnormal conditions. In the form shown, however, switch 98 is the typewhich may .be permanently closed.

interrupter and totalizing circuita-As shown and explained in my firstcopending application an interrupter generally indicated at tilt isadapt= ed to be inserted in the circuit for transmitting the control andfrequency impulses to the load adjusting motor relays. This interrupteris inserted by throwing switch 25 to its down position whereupon (lowerright corner Fig. 1) current is supplied from D. C. line. it through thelower right contact of switch 26 to the interrupter contacts which areshown as being continuously driven by a suitable motor while the otherside of this intermittently interrupted circuit is connected to wire 21leading to each of the load controllers and also leading to thecontact-making devices of each of the load controllers and frequencycontrollers. The result is that both the frequency and load controlimpulses are broken up into shorter impulses, thereby insuring morestable control and operation of the units.

The circuit for totalizing the output of all units includes (top ofFig. 1) rotatable resistances ifii, MN" and i @i'. These resistances areconnected to the same shaft with the unit load transmitters it, etc. soas to be adjusted in accordance with the output of each particular unit.To totalize the unit outputs these resistances are connected in seriesby a wire m2 leading from transformer i and connected to one end ofresistance iti, thence out through a slide contact its which isconnected to one end of resistance mi", through another slide contactwhich is connected to one end of the other resistance flili' and thenceout the slide contact thereof over to a totalizing wattmetergenerallyindicated at HM and back to transformer 115'. As the output on eachindividual unit changes, the accumulative efiect of the resistances 6M,etc. will be reflected upon the totalizing wattmeter its.

Manually initiated automatic transfer. Load to -condenser.Eacli unit isprovided with the following described equipment but for purposes ofunderstanding only one unit need be described. It.will be assumed thatthis unit is on load and is to be transferred to condenser automaticallywhen a control room push button is closed menually. See Fig. 3.

An operation selector switch iii is placed in down position and a typemlector switch lid is moved to its up position. The usual turbine gatewhether of the wicket, plunger or cylinder gate type is open. In theevent that the turbine power is adjusted through use of manually orspeed governor controlled adjustable runner blades then these may beadjusted automatically so as to assist in transferring the unit in thesame manner as though turbine gates were used alone. Adjustable runnerblades or vanes will therefore herein be considered as broadly includedas turbine gate mechanism. When the turbine gate mechanism is open, apenstock valve Mia is likewise open. This penstock valve may be of anysuitable form such for instance as a butterfly valve or the so-calledLerner-Johnson valve. It is assumed for purposes of illustration hereinthat a Lamar-Johnson valve is employed oi the type having a suitablepilot valve nose controlled plunger Hit; the pilot valve iiic beingoperated by a pinion shaft I 4! id extending laterally through the valvestructure to the exterior where a gear and pinion i i ie are providedfor either actuating the pilot valve or for indicating the position ofthe plunger. The gears Hie and pilot valve Mic are actuated by anelectric motor Hi1 which is automatically controlled in a manner to bedescribed later.

To transfer the unit from load to condenser a control room push buttonH2 is momentarily closed, whereby a relay H3 is energized and itscontacts closed by current supplied by D. C. wires lid and M5. In. viewof push button switch Hi2 being only momentarily closed, a holdingcircuit is provided from contacts of relay H3 down through the relaycontact bar and its stem to wire 6 it, across condenser contacts C2,wire 5 H, across contacts B3 and back to the coil of relay i i3 to theother side of the supply H5. A circuit is also established from supplyline i i5, across relay contacts M8, operation selector switch contactsC, thence across type selector switch contacts B2 and load limitcontacts lit to the closing field of a usual motor operated load limitmechanism such herein generally indicated at I iii from which thecircuit continues to the other supply line H5. Upon energization of thisload limit mechanism the pilot valve or any other suitable mechanism forcontrolling the gate operating servo-motor will be so actuated as tocause the turbine gate mechanism to move toward closed position. Whenthe load limit mechanism has closed to 10% opening, whereby the gateswill likewise assume a 10% opening. which is assumed for sake ofdescription herein to be speed-no-load position, contacts i it areopened automatically by the load limit mechanism thereby preventingfurther closure of the turbine gates, it being understood that theturbine gates will follow very closely any ad- Justment of the loadlimit mechanism as long as the load demand is sufficient to require gateadjustment. Any suitable mechanism may be used to efiect opening of thecontacts in accordance with the gate position or unit output but suchdevices need not be described here in detail as they have been variouslydescribed in this and other applications oimine.

Simultaneously upon establishment of the circuit through the motoroperated load limit mechanism 5 it a second circuit is established fromtype selector switch contacts B2, through wire I20, across closedcontacts itii to wire 822 to energize and close a relay Hi8, and thenceback to the other side of the D. C. line as by wire lid. Upon closure ofrelay 1123 a circuit is established from D. C. supply line lid throughwire i25, across nolly closed contacts lit to wire 82?, thence acrosscontacts 829 to wire E38 and across closed contacts iii to wires i32 andi333, across contacts of relay H233 to wire use and thence through relayits to the other side of the supply as by wire I36. Upon energization ofrelay E35 other contacts generally indicated at it? are closed toestablish a closing circuit for the usual electric motor iilf, Fig. 7,which is adapted when actuated to rotate pinion shaft 6 i id and therebymove pilot valve 8 i to to cause closure of the Lerner-Johnson valve ina manner well understood in the valve art. To insure complete closure ofthis valve when contacts i i8, iii are opened at 10% of the turbine gateposition, a holding circuit is established for relay 835 which extendsfrom wire its to wire i 39, across the closed contacts of relay i35around to its coil and wire i36.

It is therefore seen that the unit is transferred to condenser operationdue to the penstock valve being completely closed, even though theturbine gate mechanism remains at 10% gate opening.

when the penstcck valve has reached 1% opening, it closes contacts I 40.These and other contacts are operated by suitable mechanismdiagrammatically shown at I60 in the form of a disk carrying a pinadapted to successively actuate the contacts, the disc as shown in Fig.7 being secured to pinion shaft IIId. Upon closure of contacts I40 acircuit is established from an A. C. supply line I (left side Fig. 3)across condenser transfer contacts C1 to wire I42 and contacts I40,thence through a solenoid I43 to the other side of the A. C. supply.Energizatio'n of solenoid I43 opens a usual drain valve I43a, Fig. 7,preferably of the quick acting Johnson type for the turbine casing. Asolenoid I431), connected in parallel with solenoid I43 so as to beenergized simultaneously therewith, causes a usual draft tube vent I430to open, thereby unwatering the runner passage to reduce hydraulicfriction to a minimum. If desired solenoid I43 may be used to operate orcontrol only the drain valve, the draft tube vent valve being operatedby any usual mechanical connection to the gate.

The penstock valve, of course, continues toward its closing positioneven after contacts I40 are closed and upon reaching full closedposition load limit contacts I29 are automatically actuated by asuitable connection to the penstock valve. It is desired to energize thedrain valve solenoid I43 by alternating current due to the possibilityof the unit operating for a substantial period of time on condenser. Theother supply lines H4 and I I5 can be direct current, supplied ifdesired from a storage battery but circuits controlled thereby areclosed for a relatively short period.

The use of the drain valve and its coordinated operation in relation tothe other elements is found to be particularly useful in a low specificspeed. turbine where the runner blade form is such as to trap waterbetween the inlet edge of the water and guide vanes. The runner undersuch conditions acts as a pump when the unit is motored from the linethus causing excessive losses by the pressure of the water so trapped.The drain valve and draft tube vent may of course be used with propellerand high specific speed Francis types of turbines.

Manually initiated automatic transfer. Condenser to load.--When it isdesired to transfer the unit from condenser to load, operation selectorswitch .I II is moved to its up position, type selector switch I I0remaining in its up position. Upon changing the operation selectorswitch III from condenser to load, the holding circuit for relay H3 isbroken due to opening of the condenser contacts C2. However, with theoperation switch in its upper or load transfer position momentaryclosure of push button switch I I2 will cause re-energization of relay II3 and its holding circuit will again be established as by connection ofwire I I6, across contacts L2 to wire I I1, contacts B3, and thence backto the other side of the relay coil I I3. Upon energization of relay II3a circuit is established from its contacts, across load contacts Lo ofthe operation selector switch, thence along wire I44, across contacts B1to wire I 45 to energize and close a relay I 46 which is connected tothe other side of the supply line II5. Upon energization of relay I46 acircuit is established from D. C. supply II4 through wire I25, acrosscontacts I26 to wires I21, I28, across closed contacts I41 to wire I48,thence through the contact bar and its stem of a relay I49 to wire I50,across closed contacts I5I of the penstock valve limit switch to wireI52, across contacts of normally closed switch I53, up to wire I54,thence across the closed contacts of relay I46 to wire I55 whichenergizes relay I56 that is connected by wire I36 to the other side ofthe D. C. supply. Upon actuation of relay I56 another set of contactsgenerally indicated at I51 are closed so as to start opening operationof the penstock valve operating motor. When the valve has opened 1%contacts I40 are opened, thereby deenergizing drain control solenoid I43and closing the draft tube vent, thereby permitting the turbine to besubsequently properly operated. As the penstock valve continues to openwith consequent continual operation of the load limit switch I60,contacts I6I and I62 are closed at 10% opening of the penstock valve.Contacts I6I are arranged through the cam as shown to open at 60% whilecontacts I62 remain closed above 10%. Upon closure of contacts I62 acircuit is established from wire I44, across contacts B1, wire I63,contacts I62, wire I64, across normally closed contacts I65 to operatethe motor operated load limit mechanism I I9 in a direction to permitthe gate operating servo-motor to open the turbine gates in accordancewith whatever load demand there should be. Of course if the load shouldnot require more than a 10% gate opening, the gates would remain at thatopening even though the load limit is adjusted to permit full gateopening. When the load limit mechanism opens to full 100% open positioncontacts I65 are opened automatically-thereby as previously mentioned.Upon closure of contacts I62 a further circuit is established throughwire I61 to relay I49 and thence to the other side of the D. C. supply.When relay I49 is raised it breaks the circuit through wire I48, therebybreaking the circuit through wire I50 which ultimately passes throughrelay I56 as previously described, whereby upon deenergization of relayI56 its contacts open and stop operation of the electric motor for thepenstock valve. However, when the valve motor is thus stopped as byclosing contacts I62 the closure of contacts I6I initiates operation ofa hydraulic motor which continues the opening of the penstock valve.This is effected by the energization of a solenoid I68 which causesopening of the hydraulic motor that preferably is of the impulse turbinetype, this motor being provided preferably with a needle nozzle which ismechanically closed as by a spring or otherwise upon deenergization ofthe solenoid I68. The penstock valve thus continues to open and uponreaching 60% open position opens contacts I41 and closes contacts I69while at the same time opening contacts I6I but allowing contacts I62 toremain closed. Upon closure of contacts I69 current is supplied from theD. C. supply line II4, to wires I25, I21 and I28 to contacts I69, wireI10, thence through the contact bar and stem of relay I49 to wire I50,across contacts I5I, wire I52, contacts I53, wire I54, across contactsof relay I46 to wire I55, thence through relay I56 to wire I36 and theother side of the D. C. supply, thereby raising relay I56 and closing aset of contacts I51 which operate the electric motor for continuing theopening of the penstock valve. When the penstock valve is open to itsfull position, it automatically opens contacts I5I thereby stopping theactuating motor.

The hydraulic motor is used to effect the largest part of the opening ofthe penstock valve because of its greater power'with consequent fasteropening of the penstock valve. The size and cost of the electric motor,therefore, will be much smaller than if an electric motor was used alonefor effecting an equal rate of fast opening.

Exclusive manual control of transfer.-In the operation of hydraulicunits it is desirable to have suitable control means in the turbine pitso that in case an operator is in the pit and desires to shut down oropen the turbine he may effect such operation without the necessity ofgoing up to the control room to operate the push button II2. It will, ofcourse, be understood that the manual control equipment to be describednow could be located at any convenient point but it is assumed forpurposes herein that the same is located in the turbine pit.

Exclusive manual control (contd): condenser cpcration.-Type selectorswitch H is moved to its down position whereupon by closing the lowerpair of contacts of switch I53 a circuit is established from one side ofthe D. 0. supply IId through wire I25, contacts I25, wires I27, I25,across contacts I29. wire I30, across contacts I3I to wire I32, andacross the lower closed contacts of switch I53 to wire I 34 and relayI35 to wire I38 on the other side of the D. C. supply. Energization ofrelay I35 establishes a holding circuit from wires I32, I33, I39, acrossthe contacts of relay I35 to the other side of the supply. Actuation ofrelay I35 operates the contacts I3'I for the penstock motor whereuponthe valve closes in the usual way until limit switch operating mecha--nism opens contacts I29 of the penstock valve and at the same time ofcourse closes contacts I5I to render the equipment ready for reopeningof the valve. The remaining contacts such as I61, I69, I 6 I, I82, etc.are ineffective during this operation and hence consideration does notneed to be given to them.

Exclusive manual control (contd) load transer.To transfer the unit toload, the lower set of contacts of switch I III is momentarily closed,thereby establishing a circuit from D. C. supply line H4 through wireI25, across contacts I26 to wires I27 and thence to the left along wireI28, across contacts A1 of type selector switch to wire I M, acrosscontacts I M, wire I52, across upper pair of contacts of switch I 53,across the lower contacts of switch I3I, thence to wire I55 and relayI53, to wire I36 connected to the other side of the D. C. supply I I5.Upon energizatica and closure of relay I58 a'holding circuit isestablished from wire I36, across to the left contact of the closedrelay I56, thence along wire I775, across upper closed contacts ofswitch I 53, through wire I52, etc. to the other side of theD. C.supply. The contacts I 5i adjacent relay I 56 are thereupon actuated toeffect actuation of the penstock valve motor to effect opening of thevalve.

Exclusive manual control superimposed upon semi-automatic control-If thetype selector switch I I0 remains in its up position for permittingsemi-automatic control to be initiated by closure of push button II2still the turbine may be started up or shut down by the operator in thepit merely by suitably manipulating the controls just described.

For instance by simultaneously pushing switches I3I and I I6 to theirdown position a circuit is established from D. C. supply line II lthrough wire I25, across closed contacts of switch I26 to wire I21 anddown to the closed contacts I76, thence to wires I78 and I59, acrosscontacts I 5| wire I52, upper contacts I53, thence across the lowercontacts I3I to wire I55 and relay I55 to wire I36 and the other side ofthe supply. A holding circuit is established from contacts I53 to wireI15 for relay I 56. The valve is thereupon opened due to closure ofcontacts I5? for actuating the penstock valve as previously described.

To close the valve, switch I53 only need be operated. It is moved todown position whereupon a circuit is established from one side of thesupply through wire I25, contacts I 26, wire I21, I28, contacts I29,wire I30, upper contacts ISI. wire I32, and across the lower contactsI53, wires I36 and relay I35 to wire I36 and the other side of the line.Contacts I37 are thereupon closed to effect actuation of the valve. Aholding circuit is also established as by wire I39.

Transfer from condenser to load automatically upon occurrence of lowjrequency.As previously stated each generating unit is provided with theequipment shown in Fig. 3. Assuming that one unit is on load and twounits are on condenser and that it is desired to have one of thesecondenser units transferred to load automatically upon occurrence of apredetermined low frequency, the operation selector switch III and thetype selector switch I I0 each for that particular unit will be placedin their upper position. It is desired that the other condenser unitshall remain on condenser and not be transferred. To accomplish this itsoperation selector switch is placed in down or condenser position whilethe type selector switch for this unit may be in either position.

The result is that upon occurrence of a predetermined low frequency(upper left corner Fig. 1) contacts I80 of a usual frequency recorderdiagrammatically indicated at FR will close, thereby establishing acircuit from one side of the D. C. supply IIII through wires I8I, acrossclosed contacts L1, wire I82 and relay II3 to energize and close thesame. Energization of relay H3 establishes the same circuits as whenpush button switch I I2 was closed. The unit will, therefore, betransferred automatically to load upon occurrence of a predetermined lowfrequency while any other unit, even if on condenser butwith its operation selector switch remaining in condenser posi tion, will not betransferred. However, if these other condenser units have theiroperation selector switches in automatic position then they too will beautom tically transferred with the other condenser unit. It will, ofcourse, be understood that generally it is not desired to have more thanone unit on condenser for the sake of economic operation. A unit whenonce transferred to load will remain on 102; even though normalfrequency is restored, this being due to the holding circuit for relayII3. Lights are provided for indicating the type of operation for whichthe switches I I0 and I I I are set.

Feed-back prevention arrangement to permllt simultaneous transmission ofload and frequency control impulses.In the arrangements previouslydescribed in this or other applications, means have been especiallyprovided to permit simultaneous operation of the frequency and loadcontrollers without interference between the frequency and load controlimpulses. This special means consisted primarily of contacts operated ina fixed relation with respect to other contacts. With such anarrangement the load control impulses were definitely bgoken, duringwhich broken period the frequency control impulses were transmitted,thereby causing alternate transmission of the impulses.

In the modified arrangement to be described now, the frequency and loadcontrollers are not operated in any fixed mechanical relation but area,o1o,sc4 permitted to operate independently and even though theirrespective impulses might be simultaneously createdand transmitted,still only one or the other will finally be effective upon the loadadjusting motor. In this way not only are the controllers simultaneouslyoperative but also the impulses are simultaneously transmitted, and infact simultaneously imposed upon the load adjusting motor. Due to myimproved feed-back prevention the load and frequency control imtrollersfor units I--3 are shown at L'--L while the load adjusting orsynchronizing motor relays are shown at 28, 35', etc., these referencenumbers corresponding to the elements of the same numbers in thepreferred form. If the frequency variation falls below normal then theoscillatable contact bar 200 of the frequency controller F transmitsintermittent impulses through wire 2! to a common bus 202, which isconnected through resistances 203, 203", etc., to wires 204, etc.thereby energizing raising relays 35', 35", etc., from which the currentreturns to the other side of the supply wire 33. If the frequencyvariation is such as to necessitate lowering of the output, thenfrequency control impulses are transmitted through wire 205 too. commonbus 206, from which the impulses are transmitted through resistances201', 201", etc. and down through wires 208, etc. to the lowering relays28', etc. So far it is seen that the frequency correction impulses willcause actuation of the relays 28' or 35', etc. in the manner to electproper correction of the frequency.

To permit simultaneous transmission of the load control impulses theload controllers such as L' are connected to the wires 2 and 208' on theinside of the resistances 203 and 201 with the result that should alowering frequency impulse be transmitted through wire 208' so as toclose relay 28' simultaneously with the operation of a raising loadcontrol impulse through wire 2" to close relay 35, it is seen that theload adjusting motor would simply be neutral and held against rotationin either direction. If the load controllers and frequency controllershad the same rate of rotation then there is of course the possibilitythat the lowering frequency impulses would occur simultaneously at alltimes with the load raising impulses thereby resulting in the loadadjusting motor never being actuated, but in practice the frequency andload controllers will not maintain absolute synchronism with each othereven though driven at the same rate although in order to positivelyprevent continuous simultaneous transmission of the opposing impulsesthe load controllers may be operated faster than the frequencycontrollers or vice versa.

However, it is seen that when one of the controllers momentarily doesnot transmit its impulses the impulses from the other controller maythen be instantly effective to actuate the load adjusting motor.

To insure that the load controller for one unit will be effective onlyon that unit even though it is electrically connected to the circuitsfor the other units, the resistance 20! has suflicient electricalresistance so that in combination with the electrical resistance ofresistance 203" or 203' any load control impulse which tends to betransmitted from the raising cam 205' will have its current sufllcientlyreduced in passing through the combined resistances 203' and 203 that itwill be unable to sufficiently energize relay 35" to close the same. Thesame is also true of the other resistances 201, 201" and 201'.Therefore, it is seen that the raising or lowering impulses of the loadcontroller of one unit will not affect the other units, and yet at thesame time the frequency control impulses may be readily transmitted toeach of the units. It can be seen from the foregoing that in case thefrequency drops, raising impulses are transmitted to each unit andsimultaneously and in addition the load is redistributed between thevarious units in accordancewith a predetermined schedule of operation,preferably the economic schedule. This redistribution is effected due tothe unit wattmeters or other unit load indicating devices causing thegalvanometers of each unit to either raise or lower the output of theirrespective units.

Modification of feed-back prevention. Relay control.In Fig. 4 thefrequency and load controllers are not mechanically connected and yetmeans are provided for positively preventing simultaneous transmissionof load and frequency control impulses to the relays of the loadadjusting motor. In this modified form either one impulseor the other isgiven an unrestricted path to the raising and lowering relays. Toaccomplish this a wire 2l5 from the lowering side of a frequencycontroller is connected to a contact M6 and also to the coil of a relay2H which is connected to the other side of the supply. A second contact2|! is connected to the lowering side of the load controller L while thestem of the relay contact bar is connected through a flexible lead M9 tothe lowering relay coil 28'. When a load control impulse is transmittedto contact 2i! from controller L', the impulse will continue through therelay stem to the lowering relay 28' and actuate the load adjustingmotor 3 l accordingly. A frequency impulse cannot be impressedsimultaneously upon relay 28' because contact H6 is open. However, if afrequency impulse is created it will energize relay 2" and raise thesame to close contact 2" whereupon the frequency impulse will betransmitted to relay 28-. When contact 2" is thus closed, load contact2|! 'is opened to prevent transmission of load control impulses. Thefrequency impulses therebytake preference over the load control impulsesdue to controlling the coil of relay 2 I 1' although it is clear thatthe load impulses could be used to energize relay 2| 1' instead offrequency impulses. The other half of the control circuit and relays isnot shown but it would simply duplicate the first half and the wholewould be duplicated for each unit.

modiflcatirm.In this arrangement means are provided for requiring only asmall current to flow through the controller contacts and yet permittingthe necessary current for the relays. This arrangement may be employedwith any of the previously described controls in that wires 22!! and 22!correspond to the raising and lowering wires such as 206 and 202 leadingto the load adjusting motors. These wires here however are supplied bycurrent from a separate source 223. When a lowering frequency impulse istransmitted Irom irequency controller such as F it will energize a relay224 to close contacts 225 and allow current to be supplied to wire 220or 9. raising impulse will energize a relay 226 to close contacts 221and supply wire 22 i. This control is duplicated for each unit.

Instead of operating a unit or' units as condensers for purposes ofpower factor correction or for carrying a portion of the wattlesscurrent, the unit can be kept in parallel with the system with varyingamounts of excitation so that little or no condenser efiect is present,thus causing the machine to be merely held in reserve for generatingservice.

Selector switches SM and 362, shown immediately above the left end ofirequency recorder FR, have been included to automotically indicate theconnection of the frequency recorder to any one of the three unitpotentials corresponding to the three generating units 9, 2 and 3 asshown in Fig. 2. The connection from these frequency recorder selectorswitches 3M and 302 can be made in any desired manner as tall and 392are connected in parallel with F, F", F' respectively through switches882 88 88".

It will of course be understood that while several forms of my inventionhave been shown and described along with several functions performedthereby, yet other functions may be performed and various changes may bemade without departing from the spirit of the invention as set forth inthe appended claims.

I claim:

1. A control system for a plurality oi prime mover operated alternatingcurrent generating units normally connected in parallel to a main systemand from which a plurality of customers or sub-systems are supplied,means for distributing the load between said units automatically inaccordance with a predetermined schedule of operation, means fordisconnecting one of said units from the main system and supplying anindividual customer or sub-system from. said disconnected unit, andmeans whereby upon said disconnection said automatic means fordistributing the load between all of the units is rendered inoperative.

2. A control system for a plurality of prime mover operated alternatingcurrent generating units normally connected in parallel to a main systemand'from which a plurality ofcustomers or sub-systems are supplied,means for distributing the load between said units automatically inaccordance with a predetermined schedule of operation, means fordisconnecting one of said units from the main system and supplying anindividual customer or sub-system from said disconnected unit, and meanswhereby upon the disconnection of said unit from the system line all ofthe units are automatically placed on independent base, load.

3. A control system for a plurality of prime mover operated alternatingcurrent generating units normally connected in parallel to a main systemand from which a plurality of customers or sub-systems are supplied,means for maintaining all of said units'on station base load, meansincluding usual circuit breaker apparatus for disconnecting one of saidunits from the main system line in order to supply an individualcustomer or sub-system from the disconnected unit, and means wherebyupon opening 01 said circuit breaker all oitheunits are automaticallytransferred to independent base load.

4. A control system tor a plurality of prime mover operated alternatingcurrent generating units normally connected in parallel to a maindividual customer or sub-system from the dis- I connected unit, andmeans whereby upon said disconnection of the unit from the main systemall of the units are automatically placed upon independent base load,said latter means including unit load setters which are automaticallysub- 3 stituted for said master load setter upon the transfer toindependent base load.

5. A control system for a plurality of prime mover operated alternatingcurrent generating units normally connected in parallel to a main systemand from which a plurality of customers or sub-systems are supplied,means including a master load setter for distributing the station loadbetween all of said units automatically in accordance with apredetermined schedule of operation, means for disconnecting one of saidunits from the main system in order to supply an individual customer orsub-system from the disconnected unit, means whereby upon saiddisconnection of the unit from the main system all of the units areautomatically placed upon independent base load, and means wherebyanother unit may be subsequently disconnected from the main system inorder'to supply another customer or subsystem without changing the baseload control of the units as initiated upon disconnection of the firstunit.

6. A control system for a plurality of prime mover operated alternatingcurrent generating units normally connected in parallel to a main systemand from which a plurality of customers or sub-systems are supplied,means for effecting a predetermined load distribution between all ofsaid units when connected to the main system automatically in accordancewith a predetermined schedule of operation, means whereby upondisconnection of a unit from the main system in order to supply anindividual customer or subsystem the units are automatically placed uponindependent base load, and means whereby upon variation in frequencyfrom normal on said disconnected sub-system the unit supplying saidsystem is automatically transferred from independent base load tofrequency control.

7. A control system-for a plurality of prime mover operated alternatingcurrent generating units normally connected in parallel to a main systemand from which a plurality of customers or sub-systems are supplied,means for efiecting a predetermined load distribution between all ofsaid units when connected to the main system automatically in accordancewith a, predetermined schedule of operation, means whereby upondisconnection of a unit from the main system in order to supply anindividual customer or sub-. system the units are automatically placedupon independent base load, and means adapted upon a predeterminedvariation in frequency from normal on said sub-system to permanentlytransfer the sub-system unit from independent base load to frequencycontrol whereby the unit remains on frequency control even uponsubsequent restoration of normal frequency.

8. A control system for a plurality of prime mover operated alternatingcurrent generating 75 units normally connected in parallel to a mainsystem and from which a plurality of customers or sub-systems aresupplied, frequency controlling means for said units, means whereby saidunits are placed on independent base load automatically upondisconnection of one of said units from the main system in order forthat unit to supply an individual customer or sub-system, and meanswhereby said frequency controlling means is rendered unable to controlthe units which remain connected to the main system.

9. A control system for a plurality of prime mover operated alternatingcurrent generating units normally connected in parallel to a main systemand from which a plurality of customers or sub-systems are supplied,frequency controlling means for said units, means whereby said units areplaced on independent base load automatically upon disconnection of oneof said units from the main system in order for that unit to supply anindividual customer or sub-system, means whereby said frequencycontrolling means is rendered unable to control the units which remainconnected to the main system, and means whereby upon variation infrequency from a predetermined value on the disconnected sub-system theunit supplying the same is automatically connected to said frequencycontrolling means.

10. A control system fora plurality of prime mover operated alternatingcurrent generating units connected in parallel comprising, incombination, a galvanometer type of load controller for each of saidunits, a frequency controller, means including said load controllers foreffecting a predetermined load distribution between all of said units,and means whereby the galvanometer circuit for the load controller ofone of said units is adapted to be shunted out and said frequencycontroller substituted so as to cause said unit to control frequency.

11. A control system for a plurality of prime mover operated alternatingcurrent generating units connected in parallel comprising, incombination, load adjusting mechanism for each of said units, load andfrequency controlling mechanisms of a type adapted to transmit electriccontrol impulses, and a single set of relays associated with each loadadjusting mechanism adapted to receive both frequency and load controlimpulses.

12. A control system for a plurality of prime mover operated alternatingcurrent generating units normally connected in parallel to a main systemand from which a plurality of customers or sub-systems are supplied,load and frequency cdntrollers one for each unit, means whereby all ofsaid units are adapted to be placed under interconnected load controlwith the load controllers in use and the frequency controllers out ofuse, means whereby said units are adapted to be segregated forindependent connection to separate customers or sub-systems, andmanually operable selector switch apparatus adapted upon manualadjustment to establish independent frequency control for each unitafter the units are segregated.

13. A control system for a plurality of fluid actuated prime moverelectrical generating units each having a supply pipe for the actuatingfluid,

a valve in said pipe and mechanism for controlling flow of actuatingfluid directly to the prime mover, means adapted when initiated tooperate one of said pipe valves and its controlling mecha-- nism so asto transfer its generating unit from load to condenser operation, andmeans for thereafter effecting a redistribution of load between saidunits.

14. A control system for a plurality of fluid actuated prime moverelectrical generating units each having a supply pipe for the actuatingfluid, a valve in said pipe and mechanism for controlling flow ofactuating fluid through the prime mover, means adapted when initiated tooperate one of said pipe valves and its controlling mechanism so as totransfer its generating unit from condenser to load.

'15. A control system for a plurality of hydroelectric generating unitseach driven by a hydraulic turbine provided with adjustable turbine gatemechanism, a penstock and penstock valve, comprising, in combination,means adapted when initiated to eifect transfer of one of said unitsfrom load to condenser while allowing another of. said units to remainin operation including means whereby the turbine gate mechanism of thetransferred unit is moved toward closing position and the penstock valveis completely closed automatically when said initiation is eifected, andmeans whereby upon occurrence of said transfer operatic-n the load isredistributed.

16. A control system for a plurality of hydroelectric generating unitsdriven by hydraulic turbines each provided with adjustable turbine gatemechanism, a penstock and penstock valve, comprising, in combination,means adapted when initiated to effect only partial closure of theturbine gate mechanism and complete closure of said penstock valve forone of said turbines, and means for thereafter redistributing the load.

1'7. A control system for a plurality of hydroelectric generating unitseach driven by a hydraulic turbine provided with adjustable turbine gatemechanism, a penstock and penstock valve, comprising, in combination,means adapted when initiated to effect closure of the turbine gatemechanism of one of said units only to speedno-load position andcomplete closure of saidpenstoek valve, and means for thereafterredistributing the load.

18. A control system for a plurality of hydroelectric generating unitseach driven by a hydraulic turbine provided with adjustable turbine gatemechanism, a penstock and penstock valve, comprising, in combination,means adapted when initiated to efiect only partial closure of theturbine gate mechanism of one of said units and complete closure of saidpenstock valve for said unit whose gate mechanism is partially closed,means whereby upon a predetermined closing movement of said mnstockvalve the turbine is automatically vented, and means whereby the load isredistributed automatically upon occurrence of said closing operation.

19. A control system for a plurality of hydroeectric generating unitseach driven by a hydraulic turbine provided with adjustable turbine gatemechanism, a penstock and penstock valve, comprising, in combination,means adapted upon initiation to effect closure of the turbine gates forsaid unit whose gate mechanism is partially closed automatically to apredetermined position in which position the gates remain, said meansincluding hydraulic and electrical apparatus sequentialiy operative toclose the penstock valve, and means whereby the load is redistributedautomatically upon occurrence of said closure operation.

20. A control system for a plurality of hydroelectric generating unitseach driven by a hydraulic turbine provided with adjustable turbine gatemechanism. a'penstock and penstock valve, comprising, in combination.means adapted upon initiation to transfer one of said units fromcondenser to load including means for opening the penstock valvethereof, means whereby upon a substantially predetermined opening of thepenstock valve said turbine gate mechanism is adapted to be adjustablein accordance with the load demand, and means whereby the load'isredistributed automatically upon occurrence of said closure operation.

21. A control system for a plurality of hydroelectric generating unitseach driven by a hydraulic turbine provided with -adjustable turbinegate mechanism, a penstock and penstock valve, comprising, incombination, means adapted upon initiation to transfer one of said unitsfrom condenser to load including means for opening the penstock valvethereof, means whereby upon a substantially predetermined opening of thepenstock valve said turbine gate mechanism is adapted to be adjustablein accordance with the load demand, means whereby when the penstockvalve has a predetermined opening the turbine vent is closed, and meanswhereby the load is redistributed automatically upon occurrence of saidclosure operation.

22. A control system for a plurality of hydroelectric generating unitseach driven by a hydraulic turbine provided with adjustable turbine gatemechanism, a penstock and penstock valve, comprising, in combination,means adapted when initiated to close the penstock valve of one of saidunits completely and to partially close the turbine gates thereof,including hydraulic and electric motors for effecting actuation of thepenstock valve at different rates, and means whereby the load isredistributed automatically upon occurrence of said closure operation.

23. A control system for a plurality of hydroelectric generating unitseach having a low specific speed hydraulic turbine provided with a wheelcasing, guide vanes and a water-wheel whose blades are so shaped thatwater is adapted to be trapped between the wheel and guide vanes whenthe unit is motoring from the line, a draft tube, a penstock and apenstock valve, comprising, in combination, means adapted when initiatedto eifect automatically closure of one of said penstock valves of one ofsaid units, draining of the wheel casing of said unit to permitdischarge of any water tending to be trapped, and venting of the drafttube of said unit whereby the wheel may rotate freely in air, meansadapted when initiated to eifect automatically a relatively slow rate ofpriming of the wheel case by gradual opening of said penstock valve andthen subsequently effecting a fast rate of opening thereof, and meanswhereby the load is redistributed automatically upon occurrence of saidclosure operation.

24. A control system for a plurality of hydroelectric generating unitseach driven by a hydraulic turbine provided with adjustable turbine gatemechanism, a penstock and penstock valve, comprising, in combination, aload limit mechanism one for each of said units for controlling theoperation of the turbine gate mechanism for its respective unit, andmeans for controlling the penstock valve of the respective units also byits load limit mechanism, and means whereby the load is redistributedautomatically upon occurrence of said closure operation.

25. A control system for a plurality of prime mover operated electricalgenerating units, means for transferring a unit from load to condenser,and means whereby an additional unit or units may be similarlytransferred simultaneously with said other unit.

26. A control system for a plurality of prime mover operated electricalgenerating units comprising, in combination, load and frequency controlmeans, load adjusting means associated with each unit and subject to thecontrol of said frequency and load controlling means, and means wherebyfrequency and load control electrical impulses may be simultaneouslycreated by and transmitted from the load and frequency control means tosaid load adjusting mechanism while allowing certain of the impulses topredominate.

27. A control system for a plurality of prime mover operated electricalgenerating units comprising, in combination, load adjusting mechanismfor each of said units, frequency and load controlling means adapted totransmit electrical control impulses to a load adjusting mechanism,including a common circuit for both frequency and load impulses buthaving provision whereby one kind of said impulses is prevented fromfeeding back so as to interfere with the other.

28. A control system for a plurality of prime mover operated electricalgenerating units comprising, in combination, load adjusting mechanismfor each of said units, frequency and load controlling means adapted totransmit electrical control impulses to a load adjusting mechanism,including a common circuit for both frequency and load impulses buthaving electrical resistances arranged so that one kind of said impulsesis prevented from feeding back so as to interfere with the other.

29. A control system for a plurality of prime mover operated electricalgenerating units comprising, in combination, load adjusting mechanismfor each of said units, frequency and load controlling means adapted totransmit electrical control impulses to a load adjusting mechanism,including a common circuit for both frequency and load impulses buthaving a relay control arranged so that one kind of said impulses isprevented from feeding back so as to interfere with the other.

30. A control system for a plurality of prime mover operated electricalgenerating units comprising, in combination, load adjusting mechanismfor each of said units, frequency and load controlling means adapted totransmit electrical control impulses to a load adjusting mechanism, arelay having opposed contacts alternatively closed in accordance withwhether frequency or load control impulses are to be transmitted, andmeans whereby upon closure of either contact said load adjustingmechanism is actuated.

S. LOGAN KERR.

